Technical Field
The present invention is generally directed to phosphate prodrugs of alvocidib and use of the same for treatment of cancer.
Description of the Related Art
Cyclin-dependent kinases (CDKs) are important regulators that control the timing and coordination of the cell cycle. CDKs form reversible complexes with their obligate cyclin partners to control transition through key junctures in the cell cycle. For example, the activated CDK4-cyclin D1 complex controls progression through the G1 phase of the cell cycle, while the CDK1-cyclin B1 complex controls entry into the mitotic phase of the cell cycle. Endogenous cyclin dependent kinase inhibitory proteins (CDKIs) are known to bind either the CDK or cyclin component and inhibit the kinase activity of the complex. In many tumors such as melanomas, pancreatic and esophageal cancers, these natural CDKIs are either absent or mutated. Thus, selective CDK inhibitors may prove to be effective chemotherapeutic agents.
Alvocidib (also known as Flavopiridol) is a synthetic flavone having the following structure:
Alvocidib is a potent and selective inhibitor of the CDKs and has antitumor activity against various tumor cells lines, such as human lung carcinoma and breast carcinoma and also inhibits tumor growth in xenograft models. Alvocidib has been shown to induce arrest in both the G1 and G2 phases of the cell cycle and also inhibit polymerase II driven transcription by inhibiting CDK9. By inhibiting CDK9, which forms part of the complex known as the positive transcription elongation factor or P-TEFb, alvocidib treatment reduces the expression of key oncogenes such MYC and key anti-apoptotic proteins such as MCL1. Accordingly, alvocidib is an attractive therapeutic agent for cancer and is currently undergoing clinical trials in relapsed/refractory AML patients.
Oral administration of alvocidib has been limited by gastrointestinal toxicity and limited oral bioavailability. Further, preclinical studies suggest that prolonged exposure may be important for maximizing alvocidib's activity. Accordingly, continuous intravenous infusion schedules have been extensively explored in human trials. Alternative hybrid dosing, including an intravenous bolus dose followed by a slow infusion have also been explored, but to date there have been no reports of orally delivering a therapeutically effective amount of alvocidib.
While progress has been made, there remains a need in the art for increasing the oral bioavailability of alvocidib. The present invention fulfills this need and provides related advantages.